1. Field of the Invention
This invention relates to a new water-based adhesive formulation. Specifically, a formulation having enhanced characteristics such as excellent adhesion without heat activation. More specifically, it relates to a one-component aqueous sulfonated polyurethane adhesive formulation having enhanced properties for use in applications where use of heat for activation is undesirable or unavailable.
2. Description of the Prior Art
Aqueous polyurethane dispersions have received a great deal of attention recently. These dispersions are compatible with many other water-based polymers, and adhesives made from them usually exhibit improved performance. Examples of these activities can be found in JP 57030776 and JP 83046277. These patents disclose heat curing, water-resistant and stable adhesive compositions comprising dispersions of partially saponified polyvinyl acetate, aqueous solutions of polyurethanes and dispersable polyisocyanate compounds. The adhesive properties of these compositions are generated with a heat curing cycle.
JP 6256749 discloses another adhesive composition prepared by adding polyisocyanate crosslinking agents to a blend of aqueous polyurethane resins and polyvinyl latex. This polyurethane based adhesive composition is reported to exhibit high adhesion, and excellent heat and water resistance.
German Utility Model patent no. 9304018 discloses an adhesive comprising at least a two component polyurethane dispersion having a pot life of 12 hours. This water-based formulation describes a polymer blend of polyurethane dispersions, EVA's or methacrylic derivatives, characterized in that it comprises one essentially non-hydrophobic plasticizer.
A draw back for these prior art compositions is the need for heat activation, making them unsuitable for use where heat for activation is either unavailable or destructive to the substrates or parts being bonded together.
The present inventors have now discovered a one-component sulfonated aqueous polyurethane dispersion based adhesive formulation having excellent adhesive properties, good green strength, solvent resistance, and capable of forming moisture and heat resistant bonds without heat activation.